Firing system



J. F. STRAITZ 1,953,275

FIRING SYSTEM Filed April 24, 1929 OOOOOOOOOOOOOOOGO I fi m OOQMM OQQO April 3, 1934.

m f F Patented Apr. 3, 1934 FIRING SYSTEM Application April 24, 1929, Serial No. 357,654

2 Claims.

The invention relates to improved method and means for firing a pipe still, cracking coil, or boiler, with gas or oil fuel. The object is to utilize to the fullest extent possible the entire combustion chamber, or furnace volume for evenly distributingthe heat of combustion.

The invention comprises method and means whereby the upward flow of the burning fuel and gases is facilitated in cooperation with the natural ascending convection currents and the pull created by the stack draft.

It has been found that by utilizing the greatest possible percentage of furnace volume and by firing vertically, the tendency is to establish uniform temperatures at all points in the horizontal planes of the combustion chamber. The fuel and air are directed in such a way that flame impingement is substantially averted. This is especially the case after the burning fuel has traveled several feet from the burner and has lost its jet effect. .By the maximum utilization of furnace volume, increased fuel burning capacity and thoroughness of combustion are secured.

In accordance with the present method and means, the heat of combustion is diffused evenly, that is the heat of combustion is applied with equal intensity over the entire heating surfaces exposed thereto.

It has been found that in the operation of tube stills, handling a volatile oil such as petroleum derivatives, an even and moderate heat, applied to all the exposed surfaces of the oil conveying tubes is conducive to the highest yields of desired products. By such method destructive decompositions of these valuable products into coke or other meless and often troublesome by-prod-' nets are avoided. Whereas heat concentration or severe flame impingement at certain confined areas in the heating surface as is common in the usual conventional arrangements in firing such stills, result in much trouble and waste.

For example in accordance with the now common practice of firing the stills, a flat flame .burner is provided projecting through the front wall of the furnace toward the bridge wall. In such case the flame, being flat and under high capacities, impinges on the bridge wall with detrimental results to the refractory, and also the flame tends to creep up the bridge wall and to impinge on the roof tubes in a confined area, thus causing overheating and coking in the tubes at this point.

Referring to the drawing, which illustrates merely by way of example suitable means for effecting the invention;

Fig. 1 is a vertical section on line 1, 1 of Fig. 2. Fig. 2 is a horizontal section on line 2, 2 of Fig. 1.

Fig. 3 is a fragmentary vertical section on a 1 reduced scale, showing a modification for preheating the air.

Fig. 4 is a sectional detail, on an enlarged scale.

Similar munerals refer to similar parts throu hout the several views.

In the tube still furnace shown by way of example, in the drawing, the combustion chamber 6 is separated from the passage 7, leading to the stack not shown, by the bridge wall 8. The still tubes 9 are arranged in any suitable way about and adjacent the walls of the furnace which are H remote from the burner and in the passage 7. A floor 10 is provided at the bottom of the combustion chamber 6, elevated or spaced above the foundation 11, providing an air chamber or passage 12. This passage inay be controlled in any suitable way, as for example by the valves 13. This passage 12 is shown as communicating with the outside atmosphere, as at 14, and also with any suitable source of preheated air; as for example with the passage 15 in the bridge wall 8.

The burner blocks 16 are seated in spaced relationship in the middle line of floor 10, one block being provided for each burner. Any number of burners may be used in a single furnace. A burner 17 is provided for each burner block and projects vertically through the port 23 and into flaring opening 18 in the burner block 16.' The burner 17 is suitably supported and connected by piping 19 extending through passage 12 to suitable sources of oil and steam supply, as indicated.

For admitting additional air to the combustion chamber 6, ports or passages 2d are provided in the floor wall 10 and surrounding the burnerblock 16. These ports or passages 20 may be controlled by any suitable damper arrangement, as for example the annular plate 21 supported on brackets 22, see Fig. 4, and having ports adapted to register with ports 20. This forms adjustable cans for controlling the how of auxiliary air from passage 12 to the combustion chamber 6.

The block 16 is provided with the port 23 joining the daring mouth 18 which surrounds the burner 17, and permits the inductive flow of combustion air from passage or chamber 12, with the fuel from the burner 17, to the combustion chamber 6. ihe flaring mouth 18 secures a spreading of the induced air, so that a substantial part thereof travels in lines inclined to the vertical which intermingles and cooperates with the supplemental air in forming a shield 01' envelope for preventing direct impingement of the flame upon the bridge wall and tubes. The excess or auxiliary air is admitted through the ports 20. Both air admissions may be under separate controls.

The object of admitting excess or auxiliary air through ports 20 to combustion chamber 6, is to reduce the furnace temperature and more particularly to obtain a larger volume of gases at lower temperature. This results in a more even transfer of heat in the convection section and consequently higher yields of products.

The type of fuel oil burner used in accordance with this invention may be either steam, air or mechanical atomizing. The burner tips or outlets may be such as to give a flat or fantail flame, a round or jet flame, a hollow cone or relatively short bushy flame.

In general practice, the hollow cone flame is preferred because its shape corresponds more nearly to the furnace volume and gives the requisite results.

As stated the air for combustion is admitted to the furnace through the circular opening 23 in the furnace floor, surrounding the burner. This air may be supplied by a forced draft blower, through an air preheater, such as 25, in Fig. 3, or from air cooled side walls, or from the bridge wall 8 as shown in Fig. 1 of the drawing. The air can also be admitted direct through the front wall; means being provided to regulate the quantity of this air to obtain the correct proportion for the amount of fuel being burned at any capacity.

It will also be noted that the air in the chamber or passage 12 absorbs a substantial amount of heat from the floor 10, with which it comes in contact.

The burner tip, since it projects somewhat into the furnace, and is exposed to the high radiant heat of the furnace, would tend to coke the fuel under certain conditions. Therefore means are provided, such as the water cooling jacket 24., to cool the parts where overheating would otherwise take place.

Operation In accordance with the method described, the flame formation is preferably that of a hollow cone. a flaring direction, which contributes to maintaining the flame formation. The supplemental air, introduced into the combustion chamber in.

a plurality of streams, arranged in circular formation around the flame and inclined to the lines of; travel of the flame, serve to secure a homo eneous mixture of fuel and air, to limit the flame spread, or collapse the flame at its outer margin, so that a more even distribution of the The air entering with the fuel is given,

combustible mixture throughout the combustion space is secured, regardless of the ratio of air to fuel, or of total quantity used. The action of the supplemental air streams is also to prevent direct flame impingement. The central air supply and the encircling supplemental air supply are preferably forced and separately controlled and so proportioned as first to secure and maintain ignition and preliminary burning, and then to facilitate complete combustion within the combustion space.

With this method of operation, it is possible successfully to use heating or still tubes on the front and bridge walls, or the so-called recirculation of combustion gases can be used in conjunction with it.

By arrangingthe still tubes as shown, about and adjacent to the walls of the furnace which are remote from the burner, and also in the passage to the rear of the bridge wall, a maximum combustion space is secured whereby an even and well distributed temperature is communicated to all of said still tubes.

What I claim is:

1. In an oil cracking furnace, the combination of meansfor introducing into the combustion chamber fuel and air located approximately on the medial line of said chamber floor, to produce an upwardly directed hollow flaring inverted cone shaped flame, means for introducing an enveloping stream of supplemental air also from the bottom of the combustion chamber in lines of travel inclined to the outer wall of the flame to produce a collapsing effect upon the flame at, its outer margin, and still tubes arranged about and adjacent to the outer and upper walls of the combustion chamber which are remote from the flame, whereby a maximum combustion space is provided between the, flameand the tubes.

2. In an oil. cracking furnace, the combination of means for introducinginto the combustion chamber fuel and air located approximately on the medial, line of said chamber floor, to produce an upwardly directed hollow flaring inverted cone shaped flame, means. for introducing an enveloping stream ofsupplemental air also from the bottom of the combustion chamber in lines of travel inclined to the outer wallof the flame having a collapsing. effect upon theflame at its outer margin, still tubes. arranged about and adjacent to the outer and'upper walls of the combustion chamber which are remote from the flame whereby a maximumcombustion space is provided betweenthe flame and the tubes, and adjustable neans for controlling the volume and pressure respectively of fuel and air, and of supplemental air.

' JOHN STRAITZ. 

